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The distribution of the Bullsnake lies primarily east of the Continental Divide from Canada into Montana and North Dakota, south to New Mexico, Texas, and Mexico, and east into Minnesota, Wisconsin, Iowa, and Missouri. In Wyoming it is found at elevations below 6,500 feet in the eastern third of the state, northern Yellowstone NP, and the drainages of the Wind and Bighorn Rivers. It resides in a wide variety of habitats in the grassland, sagebrush, and woodland communities of the prairie and foothills life zones. It is at home in canyons and rocky outcrops, the woodlots along riparian zones, shrublands, juniper/pine ridges, as well as around farm and ranch buildings in agricultural areas.
They are diurnal, active from late April into October, and are commonly seen hunting for prey during the early morning or late afternoon, but they may move about during the evening or night during hot weather. They kill by constriction and are opportunistic predators, feeding on a wide range of prey such as mice, ground squirrels, prairie dogs, rabbits, birds and eggs. As agile climbers, they often work their way into shrubs and low profile trees to add arboreal entrées to their dining menu.
They are a confident snake and when encountered in the field they will steadily go about their business of hunting for food or slowly move off into heavier cover. However, if threatened or alarmed they are quick to coil in an aggressive posture, striking out and emitting a long, drawn-out hiss. (Presumably this represents the bellowing of a bull—giving rise to their common name.) They may imitate the rattlesnake by vibrating their tail and flattening their head—which then becomes more triangular and viper like. Caution: they can bite quite hard when handled, but they readily become docile and will coil tightly around the arm.
They are large, heavy-bodied snakes with total lengths often over 4 feet long and rarely up to 6 feet. They have keeled and overlapping scales and the anal plate is entire. The background is cream or dull yellow with numerous large, rectangular blotches along the midline of the body, with additional smaller blotches along the sides. The blotches are tan or light brown at mid body and become a darker brown or black as they near the head and tail. The belly is white or cream with black spots on the lateral margins of every 3rd or 4th ventral plate; occasionally black spots are also found near the middle of these scales. There are black bars on the posterior margins of the labial scales on the upper and lower jaws. They are identified from the Great Basin Gopher Snake by having a triangular shaped rostral scale that is higher than it is wide.
Mating takes place just after emerging from the den in early spring. Males may lie-in-wait for females to leave the den, or they may follow pheromone scent trails left by females. The male rubs his body over the female and, if she is receptive, will bite and hold her by the neck during copulation. A clutch of 10-16 eggs is laid in June or July and will hatch after 60-80 days incubation. Sexual maturity is reached in the 3rd or 4th year.